An implanted device, such as a defibrillator, for example, detects ventricular fibrillation, and delivers one or more electrical pulses to stop the fibrillation and allow the heart to reestablish a normal sinus rhythm. In general, implantable defibrillators deliver a first pulse at a first energy level upon detecting fibrillation and, if the fibrillation is not stopped, deliver additional pulses at increasing energy levels until the fibrillation is stopped or the programmed progression of pulses has been exhausted.
It is generally required that the effectiveness of a defibrillator in ending episodes of fibrillation be confirmed during implantation. Any changes to the configuration and programming of the defibrillator necessary to assure its effectiveness are made at this time. For example, the energy levels or waveforms of pulses delivered by the defibrillator, the sensitivity of the device to detect ventricular fibrillation, or the position of the electrodes used to deliver the pulses, can be changed as necessary to assure the effectiveness of the defibrillator.
The process of confirming the effectiveness of a defibrillator can be time consuming and labor intensive. Typically, a physician or clinician programs the defibrillator to execute an initial fibrillation detection algorithm, and programs an initial progression of defibrillation pulses to be delivered in response to a detected fibrillation. The clinician then programs the defibrillator to induce the heart to fibrillate, so that the programmed detection algorithm and pulse progression can be tested.
The defibrillator induces fibrillation by delivering a pulse during the period of vulnerability within a cardiac cycle, e.g., during or near the T-wave, delivering a high frequency pulse train, delivering direct current, or other known methods for inducing fibrillation. The clinician programs the parameters for the induction attempt, such as the timing, amplitude, or other characteristics of a T-wave shock. If the induction attempt fails, the clinician must program new parameters for another induction attempt. When an induction attempt succeeds, the defibrillator can fail to detect the fibrillation, or fail to stop the fibrillation. In such cases, the clinician must modify the detection algorithm or the pulse progression. The process repeats until successful fibrillation induction, detection, and defibrillation occur such that the effectiveness of the defibrillator is confirmed.